The invention relates to a weaving machine with a system for cutting a filling thread that is held ready for filling insertion from a filling thread already beaten into a woven fabric.
When weaving, a filling thread inserted into a shed is beaten by a reed against the fabric edge, the so-called fell line. Before the filling thread is inserted into the next shed, it is cut off on the insertion side of the shed. The filling thread awaiting insertion should be cut at a precisely defined time in order to control the length of the next inserted filling and/or the thread tension and to satisfy other conditions.
In a known weaving machine of the above described kind (European patent document 0 284 766 A1), the filling thread is cut by a mechanical cutter which contains a drive that is separate from the main machine drive and that in turn is controlled by a programmable control system.
The objective of the invention is to design the system of the above kind so that even more precise timing of the cutting can be achieved.
This problem is solved by using a laser as the cutting device.
The invention offers the advantage that such a laser can be actuated very rapidly and that as a result the cutting of the filling can be carried out in a fraction of a second. Moreover such a laser operates without mechanical components that are subject to wear, and consequently a predetermined precise cutting time can be maintained without effect of any wear. The design of the invention provides the further following advantage when the filling is made of a synthetic material, for instance a filament thread or one containing synthetic components. Such synthetic material will be slightly fused when cut so that the fibers of the filament threads of the cut ends are bonded to one another. This feature is especial advantageous in airjet looms. In airjet looms there is a danger that the filling that is kept ready in a main blowing nozzle may fray in the vicinity of its end or may unravel. If this occurs, problems will arise during the subsequent filling insertion because of the increased danger of catching of the fibers on the teeth of the reed. Also, the appearance of fabric edge opposite the insertion side would then be degraded. Therefore the invention provides an advantage with respect to airjet looms. As regards other machinery, for instance gripper looms, the invention also offers substantial advantages, in particular with regard to the accurate determination of the time of cutting.
Cutting systems in the form of lasers are basically known in the textile industry, for instance from the Italian patent 1,140,124, the Dutch patent 175,326 and the Japanese patent document 5 247 835 A. In the state of the art, however cutting systems in the form of lasers are used for fabric-severing or for loop-cutting by the forming of felt cloth.
In a further embodiment of the invention, the cutting laser shall be fitted with an optical system that converts an emitted laser beam into a flat beam.
In order that a low-energy laser shall suffice, its beam normally must be focused onto a comparatively small spot. As regards threads, such a requirement may entail problems because of the practical difficulty of precisely aligning a filling thread to be cut with the focus of the laser. This difficulty is circumvented by transforming the laser beam into a flat beam. The flat beam may be positioned so that its width direction shall run transversely to that of the thread, and accordingly positioning the thread and/or the laser will not raise problems.